From: "Tian, Kevin" <kevin.tian@intel.com>
To: Alex Williamson <alex.williamson@redhat.com>,
"Liu, Yi L" <yi.l.liu@intel.com>
Cc: "jgg@nvidia.com" <jgg@nvidia.com>,
"joro@8bytes.org" <joro@8bytes.org>,
"robin.murphy@arm.com" <robin.murphy@arm.com>,
"eric.auger@redhat.com" <eric.auger@redhat.com>,
"nicolinc@nvidia.com" <nicolinc@nvidia.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"chao.p.peng@linux.intel.com" <chao.p.peng@linux.intel.com>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>,
"Duan, Zhenzhong" <zhenzhong.duan@intel.com>,
"Pan, Jacob jun" <jacob.jun.pan@intel.com>
Subject: RE: [PATCH v2 4/4] vfio: Report PASID capability via VFIO_DEVICE_FEATURE ioctl
Date: Wed, 17 Apr 2024 07:09:52 +0000 [thread overview]
Message-ID: <BN9PR11MB5276D245515E81844B5EC1068C0F2@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20240416115722.78d4509f.alex.williamson@redhat.com>
> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Wednesday, April 17, 2024 1:57 AM
>
> On Fri, 12 Apr 2024 01:21:21 -0700
> Yi Liu <yi.l.liu@intel.com> wrote:
>
> > + */
> > +struct vfio_device_feature_pasid {
> > + __u16 capabilities;
> > +#define VFIO_DEVICE_PASID_CAP_EXEC (1 << 0)
> > +#define VFIO_DEVICE_PASID_CAP_PRIV (1 << 1)
> > + __u8 width;
> > + __u8 __reserved;
> > +};
>
> Building on Kevin's comment on the cover letter, if we could describe
> an offset for emulating a PASID capability, this seems like the place
> we'd do it. I think we're not doing that because we'd like an in-band
> mechanism for a device to report unused config space, such as a DVSEC
> capability, so that it can be implemented on a physical device. As
> noted in the commit log here, we'd also prefer not to bloat the kernel
> with more device quirks.
>
> In an ideal world we might be able to jump start support of that DVSEC
> option by emulating the DVSEC capability on top of the PASID capability
> for PFs, but unfortunately the PASID capability is 8 bytes while the
> DVSEC capability is at least 12 bytes, so we can't implement that
> generically either.
Yeah, that's a problem.
>
> I don't know there's any good solution here or whether there's actually
> any value to the PASID capability on a PF, but do we need to consider
> leaving a field+flag here to describe the offset for that scenario?
Yes, I prefer to this way.
> Would we then allow variant drivers to take advantage of it? Does this
> then turn into the quirk that we're trying to avoid in the kernel
> rather than userspace and is that a problem? Thanks,
>
We don't want to proactively pursue quirks in the kernel.
But if a variant driver exists for other reasons, I don't see why it
should be prohibited from deciding an offset to ease the
userspace. 😊
next prev parent reply other threads:[~2024-04-17 7:09 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 8:21 [PATCH v2 0/4] vfio-pci support pasid attach/detach Yi Liu
2024-04-12 8:21 ` [PATCH v2 1/4] ida: Add ida_get_lowest() Yi Liu
2024-04-16 16:03 ` Alex Williamson
2024-04-18 7:02 ` Yi Liu
2024-04-18 16:23 ` Alex Williamson
2024-04-18 17:12 ` Jason Gunthorpe
2024-04-19 13:43 ` Yi Liu
2024-04-19 13:55 ` Alex Williamson
2024-04-19 14:00 ` Jason Gunthorpe
2024-04-23 7:19 ` Yi Liu
2024-04-19 13:40 ` Yi Liu
2024-04-12 8:21 ` [PATCH v2 2/4] vfio-iommufd: Support pasid [at|de]tach for physical VFIO devices Yi Liu
2024-04-16 9:01 ` Tian, Kevin
2024-04-16 9:24 ` Yi Liu
2024-04-16 9:47 ` Tian, Kevin
2024-04-18 7:04 ` Yi Liu
2024-04-23 12:43 ` Jason Gunthorpe
2024-04-24 0:33 ` Tian, Kevin
2024-04-24 4:48 ` Yi Liu
2024-04-12 8:21 ` [PATCH v2 3/4] vfio: Add VFIO_DEVICE_PASID_[AT|DE]TACH_IOMMUFD_PT Yi Liu
2024-04-16 9:13 ` Tian, Kevin
2024-04-16 9:36 ` Yi Liu
2024-04-23 12:45 ` Jason Gunthorpe
2024-04-12 8:21 ` [PATCH v2 4/4] vfio: Report PASID capability via VFIO_DEVICE_FEATURE ioctl Yi Liu
2024-04-16 9:40 ` Tian, Kevin
2024-04-16 17:57 ` Alex Williamson
2024-04-17 7:09 ` Tian, Kevin [this message]
2024-04-17 20:25 ` Alex Williamson
2024-04-18 0:21 ` Tian, Kevin
2024-04-18 8:23 ` Yi Liu
2024-04-18 16:34 ` Alex Williamson
2024-04-23 12:39 ` Jason Gunthorpe
2024-04-24 0:24 ` Tian, Kevin
2024-04-24 13:59 ` Jason Gunthorpe
2024-04-16 8:38 ` [PATCH v2 0/4] vfio-pci support pasid attach/detach Tian, Kevin
2024-04-16 17:50 ` Jason Gunthorpe
2024-04-17 7:16 ` Tian, Kevin
2024-04-17 12:20 ` Jason Gunthorpe
2024-04-17 23:02 ` Alex Williamson
2024-04-18 0:06 ` Tian, Kevin
2024-04-18 9:03 ` Yi Liu
2024-04-18 20:37 ` Alex Williamson
2024-04-19 5:52 ` Tian, Kevin
2024-04-19 16:35 ` Alex Williamson
2024-04-23 7:43 ` Tian, Kevin
2024-04-23 12:01 ` Jason Gunthorpe
2024-04-23 23:47 ` Tian, Kevin
2024-04-24 0:12 ` Jason Gunthorpe
2024-04-24 2:57 ` Tian, Kevin
2024-04-24 12:29 ` Baolu Lu
2024-04-24 14:04 ` Jason Gunthorpe
2024-04-24 5:19 ` Tian, Kevin
2024-04-24 14:15 ` Jason Gunthorpe
2024-04-24 18:38 ` Alex Williamson
2024-04-24 18:45 ` Jason Gunthorpe
2024-04-24 18:24 ` Alex Williamson
2024-04-24 18:36 ` Jason Gunthorpe
2024-04-24 20:13 ` Alex Williamson
2024-04-26 14:11 ` Jason Gunthorpe
2024-04-26 20:13 ` Alex Williamson
2024-04-28 6:19 ` Tian, Kevin
2024-04-29 7:43 ` Yi Liu
2024-04-29 17:15 ` Jason Gunthorpe
2024-04-29 17:44 ` Jason Gunthorpe
2024-04-27 5:05 ` Christoph Hellwig
2024-04-25 9:26 ` Yi Liu
2024-04-25 12:58 ` Alex Williamson
2024-04-26 9:01 ` Yi Liu
2024-04-19 13:59 ` Jason Gunthorpe
2024-04-23 7:58 ` Yi Liu
2024-04-23 12:05 ` Jason Gunthorpe
2024-04-19 13:34 ` Jason Gunthorpe
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